It may seem obvious pesticides are poisonous but many homeowners handle these toxic substances with casual disregard for the potential health hazards. The ingredients in pesticides, organophosphates, to be specific, are some of the most deadly poisons in the home. Pesticide poisoning can occur after direct exposure to these chemicals, and may cause disruption of the nervous system, seizures, and other serious conditions. When using pesticides, always follow the manufacturers’ instructions and use them sparingly. If your weeds can be banished with a trowel and elbow grease, it may be better to leave the chemicals on the shelf.